The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
Hybrid electric vehicles (HEVs) and plug-in HEVs and electric vehicles (EVs) use multiple propulsion systems to provide motive power. The propulsion systems may include electric or battery powered systems that operate on power received from one or more battery packs. A battery pack may include, for example, one or more banks of high-voltage batteries (or cells). The cells are volumetric building blocks of the battery pack.
The cells of a battery pack are typically oriented in a vertical arrangement, such that terminals of the cells extend vertically upward from a top side of the batteries. In this arrangement, the terminals of the cells are accessible along an exterior side of the battery pack and can be exposed to and/or come in contact with debris or other foreign objects. This can negatively affect the performance of the battery pack.
A battery pack may include lithium ion cells. Operating temperatures of the cells can affect the lifespan and performance including charging and discharging efficiencies of the cells. A lithium ion cell may have a predetermined temperature operating range in which lifespan and performance of the cell are maximized. Temperature variations can arise between the cells of a battery pack for various reasons. For example, temperature variations can arise due to manufacturing differences between the cells, differences in locations of the cells within a battery pack, and thermal path differences of each cell relative to ambient air. For this reason, it can be difficult to maintain the cells at the same temperature.
Residual capacity of a cell can vary with change in temperature. Since there can be temperature variations between the cells of a battery pack, the cells can have different residual capacities. A cell with a larger amount of residual capacity may be over-charged, whereas a cell with a smaller amount of residual capacity may be over-discharged. This reduces the service life of the battery pack.